| 36Flatback | -- 10-02-2016 @ 1:12 PM |
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My stock 36 runs but is flat. On the left bank the end cylinders have spark, but when the plug is grounded out there is no change in engine speed. Ground the center plugs and the engine has a noticeable drop in RPM. Same on right bank except it is the opposite cylinders. I thought perhaps the carburetor was the problem, but now I am not sure. If I bring the RPM up the spark seems to get weaker, not a lot but weaker. This happened once a couple of years ago and I put a kit in the carb and it stopped. I took the carb apart and it was dirty inside, but nothing seemed out of place. Any thoughts anyone... Dave C.
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| carcrazy | -- 10-02-2016 @ 2:35 PM |
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Each barrel of your carburetor feeds four cylinders. The passenger's side barrel feeds cylinders 1, 4, 6 & 7. The driver's side barrel feeds cylinders 2, 3, 5 & 8. You can see from this that each barrel feeds the two inboard cylinders on one bank and the two outboard cylinders on the other bank. If you are experiencing cylinders missing as you describe, I would check the carburetor bore that is feeding those four cylinders and look for something blocking the main fuel circuit to that bore.
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| 40cpe | -- 10-02-2016 @ 3:10 PM |
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I seem to remember someone had a rusted spot in one of the runners allowing the cylinders to draw air instead of air/fuel mix. If the carb proves OK, remove it and check for vacuum at both carb bores in the manifold when cranking the engine over.
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| 36Flatback | -- 10-02-2016 @ 4:59 PM |
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I had figured that one barrel fed each side. I wasn't sure which was which, now I know. When I did the carb the last time it solved the problem. I guess I will have to do it again (only been about 300 miles). I did notice the carburetor had a lot of "dirt" in it. There is no filter and the car sat for several years. I use 91 octane e-free gas and that may have a cleansing effect so I may have to put an aftermarket filter on. Thanks for the information. Looks like I will have the carb off again and I will check vacuum at the manifold then. Thanks for the help. Dave C.
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| TomO | -- 10-03-2016 @ 9:18 AM |
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Check your rotor, the cylinders mentioned correspond with one tab of the rotor. Tom
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| jethro48 | -- 10-07-2016 @ 3:06 AM |
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I just recently installed a 49 merc engine into my 48 ford, and I had the same symptoms. I first thought carb as well, I swapped carbs with the one from the 48 engine and it ran the same. I performed a basic compression test and found #6 at 0psi, after removing intake I found the intake valve stuck open. This will disrupt engine vacuum in the intake manifold on the cylinders in that plane thus disturbing the air/fuel ratio. Hook a vacuum gauge up yo your engine, run it and see what it reads. If it is bouncing and fluctuating that is a good indicator of a stuck valve. then do comp test. This will either confirm or eliminate base engine problems.
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| kubes40 | -- 10-08-2016 @ 9:16 AM |
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If there is spark as mentioned, then the issue is not with the distributor , rotor or wiring. My suggestion would be to check the plugs for firing. Yeah, I know it sounds "out there" but I have seen first hand "good looking" plugs not fire. Pull one of the offending plugs at a time - hook it back in the spark plug wire and ground the plug body. Turn the engine over and see if you are having good spark. I tend to be methodical and remove one possible cause of an issue a time. Once you've eliminated the plugs by making certain THEY are firing properly, we could confidently move on with the next probable cause...
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